如果a+b+c=2根号a-1+2根号b-1+2根号c-1,
则有：
a=2根号a-1
b=2根号b-1
c=2根号c-1
解得：a=b=c=2
根号3a+根号12b+根号27c
=根号6+根号24+根号54
=根号6+2根号6+3根号6
=6根号6